This invention relates to a method of purging the ink passages of an ink jet recording device, especially a device of the type which ejects ink from an outlet towards a recording medium by the use of pressure generated by the sudden decrease of volume of a pressure chamber.
This type of recording device has already become public knowlege as can be noted from, for instance, U.S. Pat. No. 3,946,398 of E. L. Kyser. In these devices, slight differences in liquid pressure and flow resistance arising between the inlet and outlet passages are utilized to eject a drop of printing fluid such as ink and to replenish the pressure chamber. If bubbles or impurities should intermix with the ink in the passages connected with the production of liquid pressure, for example, the ink passages from the ejection orifice to an automatic valve means for controlling the supply of ink to the pressure chamber, or if impurities should stick to the orifice, the normal droplet ejection operation will be impeded, even if the particles are minute. When bubbles are intermixed, some of the pressure generated by the decrease in volume of the pressure chamber is absorbed by the bubbles and the energy to be imparted to the droplet to attain its predetermined speed is lost. Impurities in the passages or attached to the orifice, upon entering into the ejection and inlet passages, destroy the delicate relationship between the two passages as previously stated, which must be maintained for the proper functioning of the device. Such impurities cause change in ejection speed and ejection direction of the ink droplet. Because of these conditions, there arises the necessity of being able to purge the ink passages before the commencement of recording operations and upon the occurrence of the above situations.